Alternating multiblock amphiphilic copolymers of PEG and tyrosine-derived diphenols. 2. Self-assembly in aqueous solution and at hydrophobic surfaces

We present an initial study of the surfactant behavior of a new family of strictly alternating multiblock polyethers referred to as poly(DTR-PEG ether)s. These polymers consist of blocks of poly(ethylene glycol) (PEG) anddesaminotyrosyl-tyrosine alkyl esters (DTR, where R = ethyl, hexyl, dodecyl). The PEG and DTR units are linked through an ether bond, resulting in a polymer with an amphiphilic backbone and regularly spaced, hydrophobic hydrocarbon pendent chains. The associative behavior of poly(DTR-PEG ether)s in dilute aqueous solutions was investigated spectrophotometrically by the benzoylacetoanilide enolization method and by static light scattering. The critical aggregation concentration for all investigated polymers was found to be lower than the detection limit of the spectrophotometric method used (estimated at 10 - 5 M of PEG-DTR blocks). The aggregation numbers measured by static light scattering were dependent on polymer composition. The adsorption of two polymers on a model graphite surface from aqueous solution was evaluated by X-ray photoelectron spectroscopy. The shape of the adsorption isotherms was dependent on the ability of the polymer to form multichain aggregates in solution.